The present invention relates in particular to a method for providing Multicast Broadcast Services continuity towards a user equipment part of a wireless network.
In modern communication networks as the 3G Long Term Evolution (LTE) defined as part of the 3GPP standardization, user equipments can be provided with either Unicast services or Multicast Broadcast Services or both simultaneously.
Unicast services are services which foresee a transmission of data and messages towards a single destination (e.g. a single mobile terminal in the case of a wireless network). Example of Unicast services are voice call, email, surfing on the Internet . . . .
Broadcast services are services where the transmitted data are readable by any destination (e.g. all mobile terminals in the wireless network can access these data). Example of Broadcast Services could be any service which does not require any registration and are available to all. GPS could be seem as such a broadcast service.
Multicast services are a middle way between Unicast and Broadcast services. Here only a group of destinations is addressed the same data and messages. Example of Multicast services could be TV streaming based on registration (often based on a fee) at a specific provider.
In wireless networks, Unicast and Broadcast/Multicast services are each associated with a bearer specifying the corresponding configuration of the physical Layer and the layer 2 in order to fulfill Quality of Services requirements for the different services.
The bearers are mapped onto physical carriers. One carrier may support several multiplexed bearers. This can be represented by different bearers are mapped on some disjoints sub frames in a radio frame. It is foreseen that. FIG. 1 shows a radio frame where bearers of different types (Unicast service or Broadcast Multicast services) are multiplexed on the same carrier. Subframes #0, #4, #5, #9 are allocated to Unicast Services while subframes #1, #2, #3, #6, #7, #8 are allocated to Broadcast Multicast Services.
In LTE, LTE-advanced networks, the Multicast Broadcast services are often referred as MBMS (Multimedia Broadcast Multicast Services) or e-MBMS (extended Multimedia Broadcast Multicast Services). It will be clear for a person skilled in the art that the present invention can be used in the context of LTE or LTE-advanced networks as well as in the context of other wireless communication networks which show the same multiplexing of Unicast and Multicast/Broadcast bearers on the same carrier.
In some cases, it may happen that the resources required for Unicast Service bearers increase leading in a congestion situation. Here a decision has to be made if the additional resource gets granted or not. In case the resource is granted then a further decision has to be made if other bearers need to be switched off. When Unicast and Broadcast Multicast services co-exist on the same carrier, prior art solutions always privilege Unicast services and possibly discontinue the Broadcast Multicast Services in case of resource limitation.
Especially if Broadcast Multicast Service is provided on a single frequency carrier, the wireless network must provide Unicast services on the same carrier for all connected user equipments which are not capable of carrier aggregation or dual reception. Given a large portion of subframe resources would be reserved for Broadcast Multicast Service for a lot of user equipments, resource limitation may be experienced for Unicast services.
The network design could minimise such resource limitation for Unicast services on carriers which simultaneously support Broadcast Multicast Service bearers.
One way to minimise the resource limitation for Unicast Services consists in distributing Broadcast Multicast Service bearers load on multiple carriers. For example, a highly popular Broadcast Multicast Service could be provided on a carrier where only a few subframes are allocated for Broadcast Multicast Services, leaving a large portion of subframe available for Unicast Services. Consequently, resource limitation for Unicast Services would happened rarely and the congestion on Unicast traffic would be kept under control. Other available Broadcast Multicast Service should consequently be allocated to other carriers.
Even though, the network design can minimise the possible resource limitation for Unicast services on a carrier shared with Broadcast Multicast Service bearers, a particular object of the present invention is to provide a method able to resolve the limitation on Unicast Service with minimum disturbance to the user experience for Broadcast Multicast Service experience.
Another object of the invention is to provide network node as well as user equipment mechanisms to resolve the issue addressed above while ensuring a continuity of the Broadcast Multicast Service in a wireless network.